Combinations of an activating cation and a weakly coordinating (sometimes referred to as "non-coordinating") borate anion, such as in ammonium tetrakis(pentafluorophenyl)borates, are used as catalyst components in metallocene Ziegler-Natta catalysts. A number of procedures have been described in the prior art in regard to how the borate anion portion of such materials might be prepared.
European Patent Publication Nos. 505,972 and 505,997 show, for example, the preparation of tri(n-butyl)ammonium tetra(pentafluorophenyl)borate by the formation of pentafluorophenyllithium from bromopentafluorobenzene and butyllithium with the subsequent reaction of the pentafluorophenyllithium with trichloroboron to produce tris(pentafluorophenyl)boron. The tris(pentafluorophenyl)boron was then reacted with pentafluorophenyllithium to produce lithium tetra(pentafluorophenyl)borate which was isolated. The last step of the reaction was the reaction of lithium tetra(pentafluorophenyl)borate with tri-n-butylamine hydrochloride in water to produce the desired tri(n-butyl)ammonium tetra(pentafluorophenyl)borate.
Japanese Published Patent Application No. 63-238087 shows the preparation of a tetramethylammonium tetrakis fluoro-containing borate by use of a Grignard reagent. A similar Grignard route for the formation of sodium tetrakis(3,4-bis(trifluoromethyl)phenyl)borate is shown in Chem Abstracts, Vol. 112, 1990, 77273e.
Finally, PCT International Patent Publication No. WO94/00459 shows a process for producing tetrakis-fluorophenylborates by the reaction of boron trichloride with an alkali metal, alkaline earth metal or dialkylaluminum-substituted phenyl reagent which can contain either hydrogen or halogen on the phenyl ring.